Machine and method for producing cardboard tubes

ABSTRACT

Cardboard tubes producing machine, comprising means for feeding more paper or paper-like strips or ribbon-shaped material, a part of which is glued in correspondence of the lower surface thereof, for advancing and winding the said strips or ribbon-shaped material forming overlapping and staggered spirals onto a spindle ( 1 ), and cutting means for cutting the tube obtained by the advancement and winding of the strips or ribbon-shaped material on the spindle ( 1 ), thus obtaining tubular elements having a predetermined length. The machine comprises means ( 3 ), positioned upstream of the spindle ( 1 ) with respect to the advancing direction of the strips or ribbon-shaped material towards the spindle ( 1 ), distributing a predetermined amount of quick setting glue between the surfaces of the penultimate and the last strips or ribbon-shaped material wound on the spindle ( 1 ).

The present invention relates to a machine and a method for producingcardboard tubes.

It is known that a machine for producing cardboard tubes basicallycomprises:

-   -   means for continuously feeding two or more ribbon-shaped strips        made of paper or similar material, at least one strip being        provided with a predetermined amount of glue in correspondence        of one of its sides, the strips being drawn from corresponding        bobbins which are supported by the feeding means;    -   belt type means, which are positioned downstream of said feeding        means, for winding and advancing said strips onto a spindle,        forming a plurality of spirals which are overlapped and        staggered according to a predetermined staggering step, so that        the tube results from the reciprocal overlapping and gluing of        the strips which are spirally wound on the spindle;    -   means, which are positioned downstream of said spindle, for        cutting the continuous tube into elements having a predetermined        length.

Obviously, the first strip, i.e. the strip destined to directly contactthe spindle, is not glued, to avoid its adhesion to the spindle surface.

In practice, the belt means, which are positioned onto the spindledownstream of with respect to the feeding direction of the strips, drawnthe strips by exerting on them a traction force which is directedtowards the spindle and, while it is forming, the tube made by theoverlapped spiral strips advances and rotates about the longitudinalaxis of the spindle.

The intervention rate of the cutting means depends on the advancingspeed of the tube onto the spindle and on the predetermined length ofthe elements obtained from the tube.

Such a machine is described in WO 95/10400 and WO 95/10399.

One of the main drawbacks deriving from of such machines lies in acleavage of the tube in correspondence of the cut sections. Thisdrawback is even more evident when the operative speed of the machineincreases.

The main aim of the present invention is to eliminate the said drawback.

This result has been achieved, according to the invention, by providingan apparatus having the features indicated in the characterizing part ofthe independent claims. Further characteristics being set forth in thedependent claims.

Thanks to the present invention, it is possible to increase theoperative speed of the machine, i.e. the feeding speed of the stripsand, consequently, the tubes producing speed, without the aforesaidcleavage effect. Furthermore, a machine according to the presentinvention is relatively simple to make, cost-effective and reliable evenafter a prolonged service life and it may also be realized by modifyingthe existing machines, without adversely affecting the functionalitythereof, at a cost which is very low when compared with the advantageswhich are obtained.

These and other advantages and characteristics of the invention will bebest understood by anyone skilled in the art from a reading of thefollowing description in conjunction with the attached drawings given asa practical exemplification of the invention, but not to be consideredin a limitative sense, wherein:

FIG. 1 is a simplified perspective view of the strips inlet section in amachine according to the present invention;

FIG. 2 is a plan view of the device shown in FIG. 1;

FIG. 3 is a front view of the device shown in FIG. 1;

FIG. 4 is a simplified block diagram of a possible control system forthe distributor (3);

FIG. 5 is a schematic perspective view of a machine according to thepresent invention seen at a point upstream of the spindle.

Reduced to its basic structure, reference being made to the encloseddrawings, a machine according to the present invention comprises,similarly to the conventional machines:

-   -   feeding means for feeding more paper or paper-like strips or        ribbon-shaped material (N1, N2, N3), said strips unwinding from        corresponding reels (not shown for sake of clarity) supported by        the feeding means, said strips, except the first one (N1) which        is destined to directly contact the spindle (1) of the machine,        being glued in correspondence of their lower surface, i.e. the        surface destined to look at the spindle (1);    -   a spindle (1) which is longitudinally developed along the        direction of the tube to be produced, onto said spindle being        wounded the strips (N1, N2, N3) forming a plurality of        superimposed and staggered spirals;    -   belt means (2) for spirally winding said strips (N1, N2, N3)        onto the spindle (1) and advancing the tube along the spindle        axis;    -   cutting means (not shown for sake of clarity) for subdividing        the tube into tubular elements having a predetermined length.

As stated above, the feeding and gluing means acting on the strips (N1,N2, N3), the winding means and the means for cutting the tube (whichresults from the overlapping and reciprocal gluing of the stripsspirally wound onto the spindle) are known to those skilled in the artand, therefore, it is omitted a more detailed description thereof. Thegluing of the lower surface of the strips or ribbon-shaped material (N1,N2, N3) is made, according to a known technique, immediately downstreamof the reels from which the strips are drawn, i.e. before the stripsenter the tube producing machine, by means of liquid glue contained incorresponding tanks onto which the strips advance, the liquid glueexploiting its adhesive power in a relatively long time to avoid that itbecame dry along the path between the gluing station (i.e. the stationwhere the tanks containing the liquid glue are positioned) and the tubeproducing machine.

Advantageously, according to the present invention, the present machinecomprises means (3) for applying a predetermined amount of quick settingglue to the upper surface (i.e. the surface opposite to that looking atthe spindle 1) of at least one of the strips which are wound onto thespindle (1) and, more precisely, to the upper surface of at least onestrip preceding the last one.

The wording “quick setting glue” denotes a glue having a high adhesivepower acting in a short time.

For example, with reference to FIG. 2 and FIG. 3, the means (3)distribute the quick setting glue on the upper surface of the second ofsaid strips (N1, N2, N3), i.e. on the upper surface of the strip (N2)preceding the last strip (N3).

Obviously, when two strips are to be employed instead of three, themeans (3) distribute the glue on the upper surface of the first strip.

According to the example shown in the drawings, said means (3) comprisea distributor apt to distribute “hot melt” glue, whose body is solid toa fixed part (30) of the tube producing machine, in such a manner toresult slightly upstream of the spindle (1), and whose nozzle (31) lookat the upper surface of the strip to be glued (in the example, the uppersurface of the strip N2).

Alternatively, according to the present invention, the said means (3)may act on the lower surface of the last strip instead of the uppersurface of penultimate one, i.e. on the lower surface of the secondstrip if the tube is made up of two strips or on the lower surface ofthe third strip if the tube is made up of three strips. In that case,the means (3) are positioned on the other side of the strips withrespect to the configuration of FIGS. 1, 2 and 3.

In any case, according to present invention, provision is made forapplying a predetermined amount of quick setting glue (for example, a“hot melt” glue) in correspondence of the interface between thepenultimate strip and the last one.

Furthermore, advantageously, said means (3) may be activated when theadvancing speed of the strips or ribbon-shaped material (N1, N2, N3)reaches a predetermined value, so that the means (3) are operative onlywhen the advancing speed of the strips is higher than a predeterminedvalue, avoiding dissipation of glue when the advancing speed of thestrips, i.e. the tube producing speed, is so low that theabove-mentioned tube cleavage does not arise.

At this end, provision is made for a strips (N1, N2, N3) advancing speedsensor, for example an encoder (4) connected with the motor (20) drivingthe belt (2)—which determines the advancing and winding of the strips onthe spindle—and further connected with an electronic programmable unit(5) apt to receive the speed signals coming from the sensor (4) toactivate the means (3) when the speed sensed by the sensor is higherthan a programmed value.

The means (3) may distribute the glue continuously or intermittently.

As shown in FIG. 5, said means (3) may also be positioned at apredetermined distance from the spindle (1) and they may be fixed to thestructure of the means for feeding the strips or ribbon-shaped material(N1, N2, N3), said feeding means being positioned upstream of thespindle. Practically, all the construction details may vary in anyequivalent way as far as the shape, dimensions, elements disposition,nature of the used materials are concerned, without neverthelessdeparting from the scope of the adopted solution idea and, thereby,remaining within the limits of the protection granted to the presentpatent for industrial invention.

1) Cardboard tubes producing machine, comprising means for feeding morepaper or paper-like strips or ribbon-shaped material, a part of which isglued in correspondence of the lower surface thereof, for advancing andwinding the said strips or ribbon-shaped material forming overlappingand staggered spirals onto a spindle, and cutting means for cutting thetube obtained by the advancement and winding of the strips orribbon-shaped material on the spindle, thus obtaining tubular elementshaving a predetermined length, characterized in that it comprises means,positioned upstream of the spindle with respect to the advancingdirection of the strips or ribbon-shaped material towards the spindle,distributing a predetermined amount of quick setting glue between thesurfaces of the penultimate and the last strips or ribbon-shapedmaterial wound on the spindle. 2) Machine according to claim 1characterized in that it comprises means for sensing the advancing speedof said strips or ribbon-shaped material wound on the spindle, the saidquick setting glue distributing means being driven by the said sensingmeans. 3) Machine according to claim 1 characterized in that the saidquick setting glue distributing means comprise a “hot melt” gluedistributor. 4) Machine according to claim 1 characterized in that saidquick setting glue distributing means comprise a nozzle oriented towardsthe upper surface of the penultimate strip or ribbon-shaped material. 5)Machine according to claim 1 characterized in that said quick settingglue distributing means comprise a nozzle oriented towards the lowersurface of the last strip or ribbon-shaped material. 6) Method forproducing cardboard tubes by winding a plurality of strips orribbon-shaped material onto a spindle, a part of said strips orribbon-shaped material being glued in correspondence of the lowersurface thereof, forming corresponding overlapped and staggered spirals,characterized in that provision is made for applying a predeterminedamount of quick setting glue between the surfaces of the penultimate andthe last strips or ribbon-shaped materials wound on the spindle. 7)Method according to claim 6 characterized in that said quick settingglue is distributed only when the advancing and winding speed of saidstrips or ribbon-shaped material is higher than a predetermined value.8) Method according to claim 6 characterized in that the quick settingglue is a “hot melt” glue. 9) Method according to claim 6 characterizedin that the quick setting glue is distributed on the upper surface ofthe penultimate strip or ribbon-shaped material. 10) Method according cto claim 6 characterized in that the quick setting glue is distributedon the lower surface of the last strip or ribbon-shaped material.